Common Era (CE) and Before the Common Era (BCE) are year notations for the Gregorian calendar (and its predecessor, the Julian calendar), the world's most widely used calendar era. Common Era and Before the Common Era are alternatives to the original Anno Domini (AD) and Before Christ (BC) notations used for the same calendar era. The two notation systems are numerically equivalent: "2023 CE" and "AD 2023" each describe the current year; "400 BCE" and "400 BC" are the same year.

The expression can be traced back to 1615, when it first appears in a book by Johannes Kepler as the Latin: annus aerae nostrae vulgaris (year of our common era), and to 1635 in English as "Vulgar Era". The term "Common Era" can be found in English as early as 1708, and became more widely used in the mid-19th century by Jewish religious scholars. Since the later 20th century, BCE and CE have become popular in academic and scientific publications because BCE and CE are religiously neutral terms. They are used by others who wish to be sensitive to non-Christians by not referring to Jesus, the center figure of Christianity, especially via the religious terms "Christ" and Dominus ("Lord") utilized by the other abbreviations.